Elongated drum drier with drying gas distributing ducts



June 8, 1965 H. KAMP ETAL 3,187,441

ELONGATED DRUM DRIER WITH DRYING GAS DISTRIBUTING DUCTS Filed Aug. 15, 1961 I 9 FAN HEINRICH HEMP HERBERT hfi/CHEL Y hlamm, HMA [2mm 6 2074A A-rrok/vEys //v VENTOR5= United States Patent "ice 3,1875441 ELONGATED DRUM DREER WHTH DRYENG GAS DESTRIBUTWG DUQTS Heinrich Kemp, Kreieid-Uerdingen, and Herbert Kriehel, Krefeld, Germany, assigns-rs to Buttner-Werhe Alctiem gesellschait, Krefeld-Uerdingen, Germany Filed Aug. 15, 1961, Ser. No. 131,664

7 Claims. (Cl. 34-57) 1 This invention is concerned with a method of and apparatus for operating a drier which comprises a horizontally-arranged drum-like chamber.

Driers are already known which consist essentially of a horizontally arranged drum-like chamber through whichthe material is guided from the feed end at one end wall to the discharge end by means of a helically-circulating how of hot gas. This gas flow is blown into the chamber or sucked into the chamber from a distributing duct ar-. ranged over the entire length of the chamber through a slot in the chamber wall directed tangentially to the wall. It is also known for waste gases from the drier to be returned to the drier-firing system or to a heat exchanger.

a feed device 2 and a slot 3 over its entire length, adjust able gas guide plates 4 being situated in the slot. The

. apparatus also includes a gas distributing duct 5. A pip pipe 13. The description up to this point is of a drying The disadvantage of the method of operation of these A known driers is that the hot gases are at the same temperature over the entire length of the distributing duct, so that the hot gases flowing into the drier through the said slot are at the same temperature at the beginning of the drier as they are at the end of the drier.

It is known that most materials are very sensitive to heat and that when they have already given up a fairly considerable part of their moisture they cannot tolerate too high hot gas temperatures. Therefore, it has been thought necessary to select an appropriately low temperature for the hot gases although in the first stage'of the drier they could be substantially hotter without any risk of damaging the materialsby the heat to which the latter are subjected.

-In order to obviate the resulting disadvantages, according to the invention a drier of the kind described is so operated or constructed that a proportion of the drier waste gases is branched off upstream of the firing system and is introduced into the hot gas distributing duct directly at one or more points which is or are situated at some distance from the beginning of the drier. This measure has the result that the hot gases flowing into the hot gas duct are mixed with the waste gases at some distance from the beginning of the drier and, as a result, are cooled to a temperature which no longer harms the material. Thus, it is possible to operate the drier in such a way that at the beginning or feed end of the drier the material is subjected to hot gases at a relatively high temperature which is not propagated to the end of the drier.

One advantage of the invention more especially is that the possibility of operating the drier with higher hot gas temperatures considerably increases the specific evaporation performance. in addition, with readily combustible materials there is no danger of a fire which is most likely to occur in the final phase of drying. A further advantage is that a relatively large quantity of waste gas can be recovered for the drying operation.

The method according to the invention and an apparatus for carrying out the method are explained with refapparatus such as was indicated above as being known. The apparatus operates in the following manner:

The fan 9 inspires the hot gases produced in the firing system 11 through a pipe 13 into the gas distributing duct 5 and thence through the slot 3 into the drying chamber 1. Owing to the tangential arrangement of the slot 3, the gases are given a helically-circulating path of motion through the chamber. The material introduced through the feed device Z'is guided by the helically-circulating flow of gas through the chamber and discharged through the pipe 6 into the material separator 7. The waste gases separated in the latter from the material are partly conducted into the firing system 11 and partly conducted through the branch pipe 12 into the open air. By adjusting the gas guide plates 4 it is possible to give the helical path of travel of the circulating gas a greater or smaller pitch and thus to lengthen or shorten the duration of the time the material is in the chamber 1.

As already mentioned, with this known method of operation or construction of the drier there is the great disadvantage that the hot gases introduced into the hot gas distributing duct 5, e.g., at a temperature of 600 C., are at the same temperature over the entire lengh of the duct so that they enter the drying chamber 1 at the same high temperature both at the beginning and in the middle of the chamber and also at the end of the chamber.

According to the present invention a proportion of the drier waste gases is branched 01f upstream of the firing system and introduced directly at one or more points into the hot gas distributing duct 5, these points being situated at some distance from the beginning of the drier. As shown in the drawing, therefore, branch pipes 14 and 15 are connected to the waste gas pipe 10. The waste gases introduced through the branch pipes directly into' the hot gas distributing duct 5 are mixed with the hot gases which are inspired from the firing system 11, e.g., at a temperature of 600 C., and cool the latter so much that in the final phase of drying the material cannot be damaged owing to excessive heat. Upstream of this mixing point, on the other hand, the hot gases enter the drier from the hot gas distributing duct 5 at a high initial temperature of 600 C., for example, so that intensive evaporation of water is guaranteed in this region.

By adjusting throttle valves 16 in the pipes 14 and 15 it is possible to vary optionally the quantity of waste gases supplied directly to the hot gas distributing duct. Similar throttle valves 16 are also provided in the distributing duct 5; one being positioned upstream of the branch pipe 15 and the other positioned between the branch pipes 14 and 15. These valves provide for reducing the flow of high temperature gases from the firing system into the area toward the exit end of the drum 1. By manipulating the valves 16 in the branch pipes 14 and 15 and the valves in the duct 15, the temperature along the length of the drum can be controlledas desired. If the valves 16 in the duct 5 are partially closed and the valves in branch pipes 14 and 15 opened, a greater amount of waste gas from the duct 10 and a smaller amount of hot gas from the firing system 11 are utilized with resultant lowering of temperatures in the drum. This is highly desirable when the drum is used for drying many Patented June 8, 1965" different materials having critical dry temperatures, and is beneficial in reducing fuel and operating costs. Additionally, the valves 16 in the duct 5 enable an operator to control the temperatures along the length of the drum. Bypartially closing these valves, the high temperatures in the can be more or less confined to the entry end of the drum. This is highly desirable since materials entering the dum at the entry end through the feed device 2 may contain high amounts of moisture which can be removed rapidly by high temperature gases without danger of burning or damaging the material. As the moisture is removed and the materials pass toward the exit end of the drum, they cannot stand such high temperatures without damage and, thus, a lower drying drying temperature is required. Controlling of the temperatures along the length of the drum provides a solution to this problem and additionally it saves cost by utilizing the heat available from waste gases which would otherwise be lost to the atmosphere.

The firing system 11 can be of the fuel fired type wherein the combustion products are directly utilized for dry ng the materials or if the materials being dried are such that it would be harmful to expose them directly to the products of combustion, a heat exchanger type firing system can be utilized wherein the fluid used for drying is passed over hot surfaces to absorb heat which surfaces have been heated by a separate means.

We claim:

1. Apparatus for drying material including in combination an elongated drum having a material inlet adjacent one end and an outlet adjacent the other end thereof, first duct means extending lengthwise of said drum and in communication with the interior thereof along the length of said drum between said ends, heating means connected to said first duct means adjacent said one end for supplying high-temperature gases thereto, means connected to the outlet of said drum for exhausting said materials and gases within said drum including means for separating said materials and gases and having a waste outlet for the separated gases, said separated 40 gases being cooler than said high temperature gases, second duct means connected to said waste outlet and to said first duct means for supplying said cooler gases to said first duct means, and means including valve means for controlling the amount of said cooler gases and the position along the length of said drum to which said cooler gases are supplied to said drum from said first duct means.

2. Apparatus as defined in claim 1 wherein said valve means are disposed in said second duct means.

3. Apparatus as defined in claim 2 wherein valve means are also provided in said first duct means.

4. Apparatus as defined in claim 1 wherein said second duct means is connected to said first duct means by a pair of spaced apart branch ducts, said valve means comprising a separate valve in each of said branch ducts- 5. Apparatus as defined in'claim 4 including a valve in said first duct means.

*6. Apparatusas defined in claim 1 wherein said drum is cylindrical in shape and is provided with a longitudinal slot extending from end to end and in communication with said first duct means, said first duct means having side walls positioned to direct a flow of gases therefrom through said slot tangentially of said drum along its length.

7. Apparatus as defined in claim 6 wherein said first duct means is provided with a plurality of spaced apart adjustable guide means along its length for directing said tangential flow of gas into said drum at various angles relative to a radius of said drum.

References Cited by the Examiner UNITED STATES PATENTS 2,143,505 1/39 Arnold 34-.57 X

2,435,927 2/48 Manning et al. 34-57 X 2,456,674 12/ 48 Caughey 34-57 2,460,546 2/49 Steph-anoff 34-57 X FOREIGN PATENTS 1,172,910 2/59 France.

NORMAN YUDKOFF, Primary Examiner.

CHARLES C. OCONNELL, Examiner. 

1. APPARATUS FOR DRYING MATERIAL INCLUDING IN COMBINATION AN ELONGATED DRUM HAVING A MATERIAL INLET ADJACENT ONE END AND AN OUTLET ADJACENT THE OTHER END THEREOF, FIRST DUCT MEANS EXTENDING LENGTHWISE OF SAID DRUM AND IN COMMUNICATION WITH THE INTERIOR THEREOF ALONG THE LENGTH OF SAID DRUM BETWEEN SAID ENDS, HEATING MEANS CONNECTED TO SAID FIRST DUCT MEANS ADJACENT SAID ONE END FOR SUPPLYING HIGH-TEMPERATURE GASES THERETO, MEANS CONNECTED TO THE OUTLET AND OF SAID DRUM FOR EXHAUSTING SAID MATERIALS AND GASES WITHIN SAID DRUM INCLUDING MEANS FOR SEPARATING SAID MATERIALS AND GASES AND HAVING A WASTE OUTLET FOR THE SEPARATED GASES, SAID SEPARATED GASES BEING COOLER THAN SAID HIGH TEMPERATURE GASES, SECOND DUCT MEANS CONNECTED TO SAID WASTE OUTLET AND TO SAID FIRST DUCT MEANS FOR SUPPLYING SAID COOLER GASES TO SAID FIRST DUCT MEANS, AND MEANS INCLUDING VALVE MEANS FOR CONTROLLING THE AMOUNT OF SAID COOLER GASES AND THE POSITION ALONG THE LENGTH OF SAID DRUM TO WHICH SAID COOLER GASES ARE SUPPLIED TO SAID DRAIN FROM SAID FIRST DUCT MEANS. 